This area is in a perpetual state of caution, which means there are heavy patrols everywhere you go. You need to get to the south end of the ship deck, and doing so undetected is tough. Do as we suggest as quickly as possible, unless we explicitly say to stop. Timing is key if you want this to work. Start by running to the west and taking cover on the north side of the base of a stairway.

While you're hugging the stairway, two Frogs jump onto the scene. One stops on the stairs just over your head and the other start patrolling northbound via the passage on the right. Wait for the patrolling Frog to pass Snake (she'll stop just after passing you) before coming off the wall and moving south down that western passage. Immediately take cover behind a tarp wall just ahead.

The two Frogs you just sneaked by leap south over your head and begin patrolling together, coming north up the passage you're in. Stay behind the tarp wall and wait for the Frogs to walk by before quietly walking around the tarp and climbing the nearest ladder on your left. Climb to the platform overhead and then climb a second ladder from which you can sidle to the right and drop down on another platform.

From this second platform, turn southwest and dive roll over the railing to land on the vent system on the right—we found this dive easier with the camera positioned directly behind Snake. Follow the vents southward until you reach the end. From there you can dive roll to the right to land on a catwalk hugging the western wall of the ship.